Various semiconductor devices are still being developed and utilized intensively, and there is no doubt that it will continuously be in the important positions. Elemental techniques essential for the development of the semiconductor devices include forming so-called thin films such as oxide films, nitride films, and oxynitride films. While the semiconductor structure is being miniaturized rapidly, this elemental technique can never be developed without improvement in film quality and achievement of film forming of high controllability.
There have been disclosed many film forming techniques. Such already disclosed techniques include a technique for reducing or preventing charge-up damage to a formed insulating film, by simultaneously applying power having two different frequencies in a parallel-plate plasma CVD apparatus (Patent Document 1).